Important: This guide provides general information about common tests and typical reference ranges. Your individual results should always be interpreted by your healthcare provider in the context of your personal health history. Reference ranges can vary between laboratories.
How to Read a Lab Report
Most lab reports include several key pieces of information:
- Test Name: What was measured
- Your Result: The value from your sample
- Reference Range: The typical range for healthy individuals
- Flag: Indicators like "H" (high), "L" (low), or "A" (abnormal)
- Units: How the result is measured (mg/dL, mL, etc.)
A result outside the reference range doesn't necessarily mean something is wrong. Many factors can affect test results, including recent meals, medications, time of day, and lab variations.
Blood Pressure
Blood pressure is measured in millimeters of mercury (mmHg) and recorded as two numbers: systolic (top) over diastolic (bottom).
Typical Categories
- Normal: Less than 120/80 mmHg
- Elevated: 120-129/less than 80 mmHg
- High Blood Pressure Stage 1: 130-139/80-89 mmHg
- High Blood Pressure Stage 2: 140 or higher/90 or higher mmHg
- Hypertensive Crisis: Higher than 180/higher than 120 mmHg
What to know: Blood pressure naturally fluctuates throughout the day. A single high reading doesn't necessarily indicate hypertension. Your provider will typically take multiple readings over time before making a diagnosis.
Cholesterol Panel (Lipid Panel)
A lipid panel typically measures four things:
Total Cholesterol
- Desirable: Less than 200 mg/dL
- Borderline High: 200-239 mg/dL
- High: 240 mg/dL and above
LDL Cholesterol ("Bad" Cholesterol)
- Optimal: Less than 100 mg/dL
- Near Optimal: 100-129 mg/dL
- Borderline High: 130-159 mg/dL
- High: 160-189 mg/dL
- Very High: 190 mg/dL and above
HDL Cholesterol ("Good" Cholesterol)
- Low (higher risk): Less than 40 mg/dL (men), less than 50 mg/dL (women)
- Better: 40-59 mg/dL
- Best (protective): 60 mg/dL and above
Triglycerides
- Normal: Less than 150 mg/dL
- Borderline High: 150-199 mg/dL
- High: 200-499 mg/dL
- Very High: 500 mg/dL and above
What to know: Optimal cholesterol levels can vary based on your cardiovascular risk factors. Your provider considers your complete risk profile, not just individual numbers.
Blood Sugar Tests
Fasting Blood Glucose
- Normal: Less than 100 mg/dL
- Prediabetes: 100-125 mg/dL
- Diabetes: 126 mg/dL or higher
Hemoglobin A1C
A1C reflects your average blood sugar over the past 2-3 months:
- Normal: Below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
What to know: Blood sugar levels are affected by food, stress, activity, and medications. Diagnosis typically requires more than one abnormal test.
Thyroid Function
TSH (Thyroid-Stimulating Hormone)
- Typical Range: 0.4-4.0 mIU/L (varies by lab)
- High TSH: May indicate underactive thyroid (hypothyroidism)
- Low TSH: May indicate overactive thyroid (hyperthyroidism)
What to know: TSH is often the first test ordered to check thyroid function. Abnormal results may lead to additional testing of T3 and T4 hormones.
Kidney Function
Creatinine
- Typical Range: 0.7-1.3 mg/dL (men), 0.6-1.1 mg/dL (women)
GFR (Glomerular Filtration Rate)
- Normal: 90 or above
- Mildly Decreased: 60-89
- Moderately Decreased: 30-59
- Severely Decreased: 15-29
- Kidney Failure: Less than 15
What to know: GFR is calculated from creatinine and other factors. It estimates how well your kidneys filter waste. Age, muscle mass, and other factors affect these numbers.
Liver Function
Common Liver Enzymes
- ALT (Alanine Aminotransferase): Typically 7-56 U/L
- AST (Aspartate Aminotransferase): Typically 10-40 U/L
What to know: Elevated liver enzymes can have many causes, from medications to fatty liver disease to temporary illness. Mildly elevated results often resolve on their own and may warrant repeat testing.
Complete Blood Count (CBC)
A CBC measures several components of your blood:
Key Measurements
- White Blood Cells (WBC): 4,500-11,000 cells/mcL (fight infection)
- Red Blood Cells (RBC): 4.5-5.5 million cells/mcL (men), 4.0-5.0 (women)
- Hemoglobin: 14-18 g/dL (men), 12-16 g/dL (women)
- Hematocrit: 40-54% (men), 36-48% (women)
- Platelets: 150,000-400,000 cells/mcL
What to know: CBCs screen for many conditions including anemia, infection, and blood disorders. Slight variations from the reference range are often not significant.
When to Follow Up
Contact your healthcare provider if:
- Results are flagged as significantly abnormal
- You don't understand what your results mean
- You have symptoms that concern you, regardless of results
- Results are different from previous tests
- You haven't heard from your provider within the expected timeframe
Pro Tip: Keep copies of your lab results over time. Tracking trends can be more valuable than looking at single results. Many patient portals allow you to view your test history.